Deep Bed Filtration of Oilfield Produced Water
JAMES T. WALLACE, JR., Filtration Specialist
J. STUART BROWN, Manager of Engineering
DeLaval Condenser and Filter Division
Florence, New Jersey
INTRODUCTION
The City of Long Beach, California was recently awarded first prize in a national
environmental competition sponsored by Petroleum Engineering Publishing Company.
The citation pointed out that the City's Department of Oil Properties has pioneered a
program of getting the various field operators to build filtration systems and then to reinject
the filtered wastewater back underground which serves a dual purpose of eliminating a
potential pollution problem and helping to curb subsidence.
The produced oil field brine water may contain as much as 25 to 50 mg/1 of oily residue
and an equal quantity of suspended solids. The brine produced water is also deficient in
oxygen. The oily residue and solids are in such quantities that they have no significant affect
on marine life, but the oxygen deficiency would be detrimental. The application of deep bed
dual media filters as the final step before injection made the program economically feasible
by removing the majority of the contaminants and making injection into the aquifers a
reality. The DELAVAL Condenser and Filter Division is proud to have played a very
important role in this filter operation.
Prior to this proven application of the DELAVAL U H R Filter, if wastewater were to
be injected, it had to be filtered through diatomaceous earth filters which were very
expensive to operate, but which produce a fine effluent quality if properly maintained.
Extensive pilot tests on an oily wastewater from an Eastern steel mill convinced us that
the UHR Filter would produce a good effluent and could be repeatedly backwashed. We
entered into a cooperative program with one of the large producers in the Wilmington Field
at Long Beach. Bench tests which were conducted as far back as November, 1967, revealed
60 percent removal of the total suspended solids and over 50 percent removal of the free oil.
The first phase of pilot tests was conducted during the period of June to August, 1968,
using a DELAVAL UHRFilter, containing 7 sq. ft. of filtration area. The objectives of these
tests were to: 1) determine the performance of the UHR Filter when operating with flotation
cell effluent on oil field produced brine water; 2) define the optimum operating conditions
for a full scale filter plant; and 3) demonstrate the effectiveness of the backwash procedure
over a reasonably long period of time.
Upflow filtration was used in the initial series of tests. The bed consisted of
approximately two feet of graded gravel which supported approximately four feet of filter
sand having an effective size of 2 mm. An additional two foot layer of 1 mm sand was placed
on top for polishing.
Tests were conducted at a filtration rate varying from 11 to 16 gsfm. The removal
performance for oil was reasonably consistent throughout the series, but the solids removal
varied over a wide range. The total suspended solids removal averaged 62 percent with a
range of 37 to 82 percent. The oil removal averaged 77 percent with a range of 66 to 86
percent.
The average length of run was 27 hours. Runs were terminated when the increase in
dynamic head loss across the media reached about 16 ft.
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